A multidomain enzyme, with glycerol-3-phosphate dehydrogenase and phosphatase activities, is involved in a chloroplastic pathway for glycerol synthesis in \u3ci\u3eChlamydomonas reinhardtii\u3c/i\u3e

Understanding the unique features of algal metabolism may be necessary to realize the full potential of algae as feedstock for the production of biofuels and biomaterials. Under nitrogen deprivation, the green alga C. reinhardtii showed substantial triacylglycerol (TAG) accumulation and up-regulation of a gene, GPD2, encoding a multidomain enzyme with a putative phosphoserine phosphatase (PSP) motif fused to glycerol-3-phosphate dehydrogenase (GPD) domains. Canonical GPD enzymes catalyze the synthesis of glycerol-3-phosphate (G3P) by reduction of dihydroxyacetone phosphate (DHAP). G3P forms the backbone of TAGs and membrane glycerolipids and it can be dephosphorylated to yield glycerol, an osmotic stabilizer and compatible solute under hypertonic stress. Recombinant Chlamydomonas GPD2 showed both reductase and phosphatase activities in vitro and it can work as a bifunctional enzyme capable of synthesizing glycerol directly from DHAP. In addition, GPD2 and a gene encoding glycerol kinase were up-regulated in Chlamydomonas cells exposed to high salinity. RNAmediated silencing of GPD2 revealed that the multidomain enzyme was required for TAG accumulation under nitrogen deprivation and for glycerol synthesis under high salinity. Moreover, a GPD2-mCherry fusion protein was found to localize to the chloroplast, supporting the existence of a GPD2-dependent plastid pathway for the rapid synthesis of glycerol in response to hyperosmotic stress. We hypothesize that the reductase and phosphatase activities of PSP-GPD multidomain enzymes may be modulated by post-translational modifications/mechanisms, allowing them to synthesize primarily G3P or glycerol depending on environmental conditions and/or metabolic demands in algal species of the core Chlorophytes

A multidomain enzyme, with glycerol-3-phosphate dehydrogenase and phosphatase activities, is involved in a chloroplastic pathway for glycerol synthesis in \u3ci\u3eChlamydomonas reinhardtii\u3c/i\u3e

Understanding the unique features of algal metabolism may be necessary to realize the full potential of algae as feedstock for the production of biofuels and biomaterials. Under nitrogen deprivation, the green alga C. reinhardtii showed substantial triacylglycerol (TAG) accumulation and up-regulation of a gene, GPD2, encoding a multidomain enzyme with a putative phosphoserine phosphatase (PSP) motif fused to glycerol-3-phosphate dehydrogenase (GPD) domains. Canonical GPD enzymes catalyze the synthesis of glycerol-3-phosphate (G3P) by reduction of dihydroxyacetone phosphate (DHAP). G3P forms the backbone of TAGs and membrane glycerolipids and it can be dephosphorylated to yield glycerol, an osmotic stabilizer and compatible solute under hypertonic stress. Recombinant Chlamydomonas GPD2 showed both reductase and phosphatase activities in vitro and it can work as a bifunctional enzyme capable of synthesizing glycerol directly from DHAP. In addition, GPD2 and a gene encoding glycerol kinase were up-regulated in Chlamydomonas cells exposed to high salinity. RNAmediated silencing of GPD2 revealed that the multidomain enzyme was required for TAG accumulation under nitrogen deprivation and for glycerol synthesis under high salinity. Moreover, a GPD2-mCherry fusion protein was found to localize to the chloroplast, supporting the existence of a GPD2-dependent plastid pathway for the rapid synthesis of glycerol in response to hyperosmotic stress. We hypothesize that the reductase and phosphatase activities of PSP-GPD multidomain enzymes may be modulated by post-translational modifications/mechanisms, allowing them to synthesize primarily G3P or glycerol depending on environmental conditions and/or metabolic demands in algal species of the core Chlorophytes

Dynamic screening of a localized hole during photoemission from a metal cluster

Recent advances in attosecond spectroscopy techniques have fueled the interest in the theoretical description of electronic processes taking place in the subfemtosecond time scale. Here we study the coupled dynamic screening of a localized hole and a photoelectron emitted from a metal cluster using a semi-classical model. Electron density dynamics in the cluster is calculated with Time-Dependent Density Functional Theory and the motion of the photoemitted electron is described classically. We show that the dynamic screening of the hole by the cluster electrons affects the motion of the photoemitted electron. At the very beginning of its trajectory, the photoemitted electron interacts with the cluster electrons that pile up to screen the hole. Within our model, this gives rise to a significant reduction of the energy lost by the photoelectron. Thus, this is a velocity dependent effect that should be accounted for when calculating the average losses suffered by photoemitted electrons in metals.Comment: 15 pages, 5 figure

Assessing the trophic ecology of three sympatric squid in the marine ecosystem off the Patagonian Shelf by combining stomach content and stable isotopic analyses

Squid species are important components of the Southern Atlantic Ocean ecosystems, as they prey on a wide range of crustaceans, fish and cephalopods. As a result of this trophic interaction and their high abundance, they are considered reliable indicators of energy transfer and biomass in the food web. We identified Illex argentinus, Doryteuthis gahi and Onykia ingens as the most important squid species interacting on the Patagonian shelf, and used isotope analysis and stomach content identification to assess the feeding ecology and interaction of these squids in the ecosystem. Our results describe trophic interactions by direct predation of O. ingens and I. argentinus on D. gahi, and a trophic overlap of the three squid, and indicate a higher trophic level and differences in the foraging areas for mature and maturing D. gahi inferred through δ15N and δ13C concentrations. These differences were related to the segregation and different habitat of large mature D. gahi and suggest a food enrichment of C and N based on feeding sources other than those used by small maturing D. gahi and I. argentinus and O. ingens.Versión del editor1,484

Takotsubo cardiomyopathy after a dancing session: a case report

<p>Abstract</p> <p>Introduction</p> <p>Stress-induced (Takotsubo) cardiomyopathy is a rare form of cardiomyopathy which presents in a manner similar to that of acute coronary syndrome. This sometimes leads to unnecessary thrombolysis therapy. The pathogenesis of this disease is still poorly understood. We believe that reporting all cases of Takotsubo cardiomyopathy will contribute to a better understanding of this disease. Here, we report a patient who, in the absence of any recent stressful events in her life, developed the disease after a session of dancing.</p> <p>Case presentation</p> <p>A 69-year-old Caucasian woman presented with features suggestive of acute coronary syndrome shortly after a session of dancing. Echocardiography and a coronary angiogram showed typical features of Takotsubo cardiomyopathy and our patient was treated accordingly. Eight weeks later, her condition resolved completely and the results of echocardiography were totally normal.</p> <p>Conclusions</p> <p>Takotsubo cardiomyopathy, though transient, is a rare and serious condition. Although it is commonly precipitated by stressful life events, these are not necessarily present. Our patient was enjoying one of her hobbies (that is, dancing) when she developed the disease. This case has particular interest in medicine, especially for the specialties of cardiology and emergency medicine. We hope that it will add more information to the literature about this rare condition.</p

Modelling the cascade of biomarker changes in GRN-related frontotemporal dementia

OBJECTIVE: Progranulin-related frontotemporal dementia (FTD-GRN) is a fast progressive disease. Modelling the cascade of multimodal biomarker changes aids in understanding the aetiology of this disease and enables monitoring of individual mutation carriers. In this cross-sectional study, we estimated the temporal cascade of biomarker changes for FTD-GRN, in a data-driven way. METHODS: We included 56 presymptomatic and 35 symptomatic GRN mutation carriers, and 35 healthy non-carriers. Selected biomarkers were neurofilament light chain (NfL), grey matter volume, white matter microstructure and cognitive domains. We used discriminative event-based modelling to infer the cascade of biomarker changes in FTD-GRN and estimated individual disease severity through cross-validation. We derived the biomarker cascades in non-fluent variant primary progressive aphasia (nfvPPA) and behavioural variant FTD (bvFTD) to understand the differences between these phenotypes. RESULTS: Language functioning and NfL were the earliest abnormal biomarkers in FTD-GRN. White matter tracts were affected before grey matter volume, and the left hemisphere degenerated before the right. Based on individual disease severities, presymptomatic carriers could be delineated from symptomatic carriers with a sensitivity of 100% and specificity of 96.1%. The estimated disease severity strongly correlated with functional severity in nfvPPA, but not in bvFTD. In addition, the biomarker cascade in bvFTD showed more uncertainty than nfvPPA. CONCLUSION: Degeneration of axons and language deficits are indicated to be the earliest biomarkers in FTD-GRN, with bvFTD being more heterogeneous in disease progression than nfvPPA. Our data-driven model could help identify presymptomatic GRN mutation carriers at risk of conversion to the clinical stage

Environmental variables, habitat discontinuity and life history shaping the genetic structure of Pomatoschistus marmoratus

Coastal lagoons are semi-isolated ecosystems exposed to wide fluctuations of environmental conditions and showing habitat fragmentation. These features may play an important role in separating species into different populations, even at small spatial scales. In this study, we evaluate the concordance between mitochondrial (previous published data) and nuclear data analyzing the genetic variability of Pomatoschistus marmoratus in five localities, inside and outside the Mar Menor coastal lagoon (SE Spain) using eight microsatellites. High genetic diversity and similar levels of allele richness were observed across all loci and localities, although significant genic and genotypic differentiation was found between populations inside and outside the lagoon. In contrast to the FST values obtained from previous mitochondrial DNA analyses (control region), the microsatellite data exhibited significant differentiation among samples inside the Mar Menor and between lagoonal and marine samples. This pattern was corroborated using Cavalli-Sforza genetic distances. The habitat fragmentation inside the coastal lagoon and among lagoon and marine localities could be acting as a barrier to gene flow and contributing to the observed genetic structure. Our results from generalized additive models point a significant link between extreme lagoonal environmental conditions (mainly maximum salinity) and P. marmoratus genetic composition. Thereby, these environmental features could be also acting on genetic structure of coastal lagoon populations of P. marmoratus favoring their genetic divergence. The mating strategy of P. marmoratus could be also influencing our results obtained from mitochondrial and nuclear DNA. Therefore, a special consideration must be done in the selection of the DNA markers depending on the reproductive strategy of the species